Airbag systems function by employing a sensor to detect a collision event, which triggers an inflator component to inflate the airbag cushion at high pressure. As a result of this process, the airbag cushion is subjected to a sudden and violent increase in gas pressure, which is then compounded by the impact of a vehicle occupant exerting external pressure against the airbag cushion. In order for the airbag cushion to protect occupants in a vehicle, it is necessary for the airbag to exhibit high burst strength.
Heretofore, various attempts have been made to manufacture an airbag cushion that is strong, robust, and exhibits high burst strength. One generally accepted method for manufacturing such cushions is by utilizing high tenacity multifilament yarns having tenacity of greater than 8.0 grams/denier (g/den).
Japanese unexamined patent publication no. 4-5,145 teaches a non-circular airbag made from hollow weave fabrics having an axis length thereof in a direction at a bias angle of 45 degrees from the warp direction, corresponding to 70 to 95% of the axis length thereof in the warp and weft direction.
Japanese unexamined patent publication no. 4-43,143 discloses an airbag made from non-circular hollow weave fabric pieces having a longer axis in a direction inclined at a bias angel from the warp or weft direction than an axis in the warp direction of the fabric pieces.
These attempts are based on the idea that a starting point in bursting of the airbag cushion resides in a seam-joining portion in a circumferential edge portion of the cushion, and provided a cushion made from non-circular woven fabric pieces having shorter axis in a bias direction than that in the warp or weft direction, to enhance the burst strength of the seam-joining portion.
U.S. Pat. No. 5,470,106 discloses the use of a woven fabric apron at the area surrounding the inflator connection to improve burst strength. Other attempts to improve burst strength have included the use of adhesive means to reinforce the weaker areas of the airbag. U.S. Pat. No. 5,296,278 teaches that bags having yarns with tensile strength measurements of less than 8.0 g/den (approximately 70 cN/tex or centi Newton/tex) do not perform well. This reference also discloses a means for applying silicone rubber at the seams to prevent fraying of the coated fabric to prevent failure at the seams.
Most of the efforts to improve the burst strength of airbag cushions have been focused on using high tenacity yarns, occasionally in combination with some other means or method for increasing seam strength. However, none of the prior art has provided an airbag cushion having a novel seam and low tenacity yarns in combination to provide high burst strength. One advantage to using low tenacity yarns in airbag cushion applications is that low tenacity yarns generally may be manufactured or purchased at a lower cost than high tenacity yarns.